Researchers are creating advanced simulations that will provide a deeper understanding of Mars's climatic history and help to determine whether it was once able to sustain life.

An international team of researchers is developing a model of Mars's evolution that could unlock some of its long-held secrets

An international team of researchers is developing a model of Mars’s evolution that could unlock some of its long-held secrets, including whether it once harboured life.

The work is being coordinated at the French National Centre for Scientific Research in Paris by François Forget, a space scientist at the Pierre Simon Laplace Institute.

The six-year initiative, named Mars through time and supported by EU funding, is aiming to piece together different periods of the planet’s history to answer the question that has long perplexed scientists: was Mars once habitable?

«Mars was a place where life could have emerged, so it’s very fascinating,» said François, the principal investigator of Mars through time.

The researchers are trying to piece together different periods of the planet’s history. Credit: NASA

The team is working to create simulations that will provide a deeper understanding of Mars’s climatic history and help to determine whether it was once able to sustain life.

«We are trying to invent a new model, to build a virtual planet that evolves through time. It’s a super ambitious project,» said François.

The work to develop this model has been ongoing since 2019 and proved more difficult to realize than initially thought – in part because of the large amount of computing power needed. But the end is in sight.

«Now I know it’s possible. I’m convinced that soon we will have a very nice tool available to the community.»

This means we may soon be able to use this virtual time machine to transport ourselves to different periods of Martian history and understand exactly what happened to the planet and when.

Like Earth, Mars was born at the dawn of our solar system, 4.5 billion years ago. It is about half the size of our own planet and is farther from the Sun than we are. At this distance, it receives less solar radiation than Earth does.

However, evidence increasingly suggests that early in its life, Mars was a warm and wet planet much like our own.

Geological and mineralogical evidence shows that Mars once possessed a thicker atmosphere than the planet has today. Even more intriguingly, we can also see remnants of ancient lakes and seas on its surface.

Two of these are currently being explored by the NASA rovers Curiosity and Perseverance.

At some point 3 to 4 billion years ago, Mars lost its atmosphere for reasons not yet fully understood, and with it, the temperate conditions that allowed liquid water to exist on its surface.

Today the planet is barren and dry, except for water thought to be trapped under its surface, and ice that we can see frozen at its poles.

When exactly the planet was warm and wet is still an open question.

«We do not understand the climate process that allowed that,’ said François, and points out a crucial issue to be explored: «liquid water means there was a possibility of the emergence of life at the same time life emerged on Earth.»

Mars is also thought to have gone through periods of vast glaciation, carving valleys on its surface, when the atmosphere temporarily disappeared.

The model is hoping to give insight into when these periods occurred. It will be able to do that with a precision unlike any previous Mars climate models. The current models provide just a snapshot of the climate at any given moment.

«We’re trying to have a new model that can simulate the evolution of Mars for thousands or millions of years. When we do that, we can simulate the evolution of glaciers and lakes.»

To develop the model, François and his team take known information about Mars and use powerful computers to simulate the conditions on its surface that this might have led to.

For example, one known major changing factor on Mars has been its obliquity, the tilt of the planet as it orbits the Sun.

Currently, it is about 25 degrees, similar to Earth, but it has varied throughout its history from almost zero degrees to more than 60 degrees, said François. This has caused large swings in the amount of heat on Mars’s surface.

The thickness and composition of the Martian atmosphere over time is also an open question. Today the planet’s atmosphere is about 1% of the Earth’s volume, with 95% of it made up of CO2.

«We used to think that if you add enough CO2, you will have a warm climate. But that is not sufficient. There is something else that allowed a warm climate.»

The current thinking is that ancient volcanism on Mars expelled a considerable amount of hydrogen into the atmosphere, which, combined with CO2, could make a sufficient greenhouse effect. «But it’s very speculative. There is a mystery there.»

Large impacts, like collisions with asteroids or comets, could also have influenced Mars’s climate. «With our tools, we can model that.» Evidence of those impacts is visible today as craters on the planet’s surface.

While Mars is barren today, it has shown many faces in the past